"> Main Switchboard - Equipment Database

Main Switchboard

critical IMO Required 22 models total

The main switchboard receives power directly from the main and auxiliary generators and splits it into feeders for propulsion auxiliaries, distribution boards and essential services; its busbar arrangement, not the generators themselves, decides whether one fault blacks out the whole vessel.

Read more — Main Switchboard explained

What sets the main switchboard apart

The main switchboard is the single point where generated power meets the ship's distribution system. Unlike a sub-distribution board, which simply passes power on, the main switchboard carries the full short-circuit current the generators can deliver and must synchronise, share load and isolate faults between multiple sources running in parallel. Its busbar arrangement, single, split or fully segregated, determines how much of the ship stays powered when one section fails.

Main switchboard single-line arrangement
Single-line diagram of a ship main switchboard: generator breakers feed two busbar sections joined by a bus-tie breaker, with outgoing feeder breakers supplying essential services, propulsion auxiliaries and the distribution board.

Main components

Busbars and bus-tie breakers

Copper or aluminium busbars carry current between generator panels and feeder panels. A bus-tie breaker lets the switchboard be split into independent sections; opening it after a fault confines a short circuit or fire to one half of the board instead of blacking out the whole vessel.

Generator and feeder panels

Each generator has its own panel with air circuit breaker, synchronising instruments and protection relays. Feeder panels distribute to propulsion motors, thrusters, distribution boards and large individual consumers, each protected by a breaker or fuse sized and time-graded to trip before the upstream generator breaker.

Protection and monitoring

Overcurrent, reverse power, under/over voltage and under/over frequency relays protect generators from being damaged by faults elsewhere on the board. A power management system on larger vessels handles load sharing, automatic start of standby generators and load shedding of non-essential consumers when generation capacity falls short.

Selection and sizing

The board is sized to the maximum fault current the connected generators can jointly deliver, not just the running load, because breakers and busbars must survive a short circuit long enough to clear it.

  • Rated current and short-circuit withstand rating (kA) of busbars and breakers.
  • Number of generator sets to be run in parallel and the resulting maximum fault level.
  • Degree of segregation required (single section, split bus, or fully redundant for DP or safety-critical vessels).
  • Arc flash protection and internal arc classification (IAC) of the enclosure.

Regulations and class requirements

SOLAS Ch. II-1 requires at least two independent sources of electrical power and arrangements that prevent a single fault from disabling both the main and emergency systems. Class rules for electrical installations set minimum short-circuit withstand ratings, discrimination (selectivity) between breakers, and, on many newer vessels, arc fault containment requirements for the switchboard enclosure. Surveys include insulation resistance testing, breaker trip testing and inspection of busbar joints for signs of overheating.

Typical faults

FaultCauseConsequence
Loose busbar jointVibration loosening bolted connections over timeLocal overheating, discolouration, risk of arc fault
Loss of selectivityIncorrectly set or aged protection relaysUpstream generator breaker trips instead of the faulty feeder, wider blackout
Insulation breakdownMoisture or dust ingress into an aged panelEarth fault, possible arc flash on fault clearance
Failed synchronisingFaulty governor or AVR response on a generatorUnable to parallel sets, reduced available power

What to look for in a supplier

  • Type-tested design verified against the actual fault level of the installation, not a generic catalogue rating.
  • Documented selectivity study showing breaker coordination across the whole board.
  • Availability of spare breakers and relay modules matching the existing panel, since switchboards commonly stay in service for the ship's full life.
  • Clear arc flash labelling and, where fitted, verified internal arc classification.

Before working inside any panel, confirm which busbar sections are still live; a split board can leave one half energised while the other is locked out for maintenance.

5 yr
Class Survey
30 yr
Typical Lifetime

Typical Manufacturers

ABB Siemens Schneider Electric Hyundai

6 manufacturers · 22 models

ABB Marine

10
ABB Onboard DC Grid Power Distribution System
Model Number
Onboard DC Grid
ABB Marine Low-Voltage Switchboard
Model Number
MNS-Marine
ABB Marine ABB UniGear Marine Medium-Voltage Switchboard
ABB UniGear Marine Medium-Voltage Switchboard
Model Number
UniGear ZS1 Marine
ABB Marine Energy Storage System
Model Number
Marine ESS
ABB Shore Connection System
Model Number
Shore-to-Ship Connection (SSC)
Shore-to-Ship Connection (SSC)
Standard
IEC/ISO/IEEE 80005-1
Voltage Shore Side
6.6 / 11 kV
Frequency Conversion
Yes (50 / 60 Hz)
Power Range
Up to 20 MVA
Reference Ports
Gothenburg, Hamburg, Long Beach, Yokohama
Onboard DC Grid
Bus Voltage
1000 V DC
Power Rating per Bus
Up to 20 MW
Footprint Reduction vs AC
20 %
Part-Load Fuel Savings
Up to 27 %
DP Response
Faster than AC system
Approvals
DNV, LR, ABS, BV
First Reference Vessel
PSV Dina Star (2013)
ABB Marine MNS-Marine
MNS-Marine
System Voltage
400 - 690 V AC
Frequency
50 / 60 Hz
Rated Current
Up to 6300 A
Short-Circuit Withstand
65 kA / 0.3 s
Protection Class
IP54
Construction
Modular MNS withdrawable
Type Approval
DNV, LR, ABS, BV, RINA, NK, KR, CCS
ABB Marine UniGear ZS1 Marine
UniGear ZS1 Marine
System Voltage
6.6 - 12 kV
Rated Current
Up to 4000 A
Circuit Breaker
VD4 vacuum, withdrawable
Internal Arc
IAC AFLR 50 kA / 1 s
Common Applications
Cruise, LNG, FPSO, DP3 drillship
Marine ESS
Chemistry
Li-ion NMC (modular)
Energy Range
0.2 - 10 MWh
Functions
Spinning reserve, peak shave, harbour mode
Connection
DC bus via DC/DC converter
Type Approval
DNV, LR, ABS
Cooling
Liquid

Kongsberg

4
Kongsberg Low Voltage Switchgear
Model Number
Low Voltage Switchgear
Kongsberg Advanced Segment Protection
Model Number
Advanced Segment Protection
Kongsberg AC Switchgear
Model Number
Ac Switchgear
Kongsberg High Voltage Switchgear
Model Number
High Voltage Switchgear

ABB

2
ABB MNS iS Marine Switchboard unverified
System type
switchboard_lv
ABB ACS880 Marine Drive Panel unverified
System type
drive_panel

Kongsberg Maritime

2
Kongsberg Maritime AS Low Voltage Switchgear
Low Voltage Switchgear
Data sheets
Low Voltage Switchgear
Advanced Segment Protection
Advanced Segment Protection Design
Harmonics and inrush considerations

Schneider Electric

2
Schneider Prisma Marine Switchboard unverified
System type
switchboard_lv
Schneider Altivar Marine Drive Panel unverified
System type
drive_panel

Siemens

2
Siemens SIVACON Marine Switchboard unverified
System type
switchboard_lv
Siemens SIPLINK Shore Connection unverified
System type
shore_connection